Formation mechanism of fine anatase crystals from amorphous titania under hydrothermal conditions

Crystallization of amorphous titania prepared by hydrolysis of ethoxide was accelerated even by a small amount of water in the vapor phase. The existence of water promoted the change of localized structure of the amorphous titania to anatase structure, which resulted in acceleration of anatase nucleation. The anatase crystals grew in steam by solid-state epitaxial growth, but stopped growing in a short time, The growth of anatase crystals under hydrothermal conditions could be divided into the following two stages: the first stage with fast growth rate by the solid-state epitaxial growth and the second stage with slow growth rate by the dissolution and deposition process.